Okay, I have given writer/director Osgood Perkins two chances now, to show me something worthwhile in his horror films, he has not passed my smell test. I could tell ten minutes into this film that it was a stinker, but that some people were going to like it. I had almost the exact same reaction to it that I had with "Longlegs". The longer the movie went on, the less I cared about anything that was happening. The only element of this that I can say might work, are the gory deaths, which are shown in plenty of detail to satisfy anyone who only cares about how gruesome something can be.
Horror movies ought to build suspense or dread. At the very least there should be a couple of jump scares to goose us into paying attention. "The Monkey" has none of those things. The main thing driving this story is the cynicism of the characters, and the depression that every one of the main figures seems to be suffering from. Twin brothers, abandoned by their father, inherit a wind up toy monkey that appears to be cursed. That appearance is because every time the toy is wound up, when it finishes it's musical performance, someone dies a horrible and grizzly death. No one cares why, no one really talks about it, and the fact that the dad ran away from it seems to suggest that the damage could be controlled is the toy is just left alone. There is a supernatural addendum as well, the toy can reconstruct itself. Whatever.
When the twins are younger, in their early teens, one is a bully and the other is a morose wimp who is bullied not only by his brothers but by a gang of girls, for no reason whatsoever. Once they realize the danger of the toy, it gets used once in an act of revenge that backfires, and subsequently, it randomly kills some others around them. The tone of the film is supposed to be nihilistically comic, but the laughs stopped coming for me early on. I can clearly see where the turning point for me was. A minister, delivering a sermon at a funeral is shown to be a naïf idiot, for no reason except for an audience reaction, but not the audience in the church, the one in the theater. I was not amused and then spent the rest of the time continuing to be unamused. 
Theo James plays the grown up brothers in the second two thirds of the film. Timid Hal has inexplicably been married, had a child and continued to be a miserable trod upon person. The intervening twenty five years are not explained and what pushes the estrangement of Hal from his son is left up to us to imagine. Supposedly, it was to keep his son free of the curse, but why would he think he needed to do that since they were curse free for two plus decades? Bad Bill seems to want revenge, but why twenty five years go by before he seeks to extract it is also unexplained. All we know is that Bill seems to have started the Monkey curse again, and the people from their small hometown are the ones randomly paying for it. The climax of the film creates a series of grim deaths for multiple random people. In concept, some of those should be funny, but in execution, they just are there without an emotional payoff of any type.
It is clearly the directors deadpan style that does not work for me. Fans of Jim Jarmusch may like this. It reminded me of his "The Dead Don't Die". Which by the way I also did not care for, but at least it had a point of view. This is an exploitation of cynical gore effects, without a story to back them up. The main characters were unpleasant, the deaths while inventive, were not shocking or scary, they just exist in this snow globe of body parts and viscera.
